The present invention relates to rollers particularly tension rollers and to an assembly incorporating such a roller including a so-called guide bolt which is secured to a holder or the like for use as assemblies for tensioning belts for cam shafts, V-belts or the like.
Roller bearings for drawer guides and the like attached to a holder or carrier are known in which the guide bolt is provided with a plug which is secured through an opening in the holder or carrier. The roller itself is mounted and held via a slide bearing. An assembly of this type is shown in West German Design Pat. No. 7,603,166.
Another prior art design in this general field is that shown in West German Design Pat. No. 7,412,059. In accordance with this design, the tension roller and sheet metal holder assembly comprise a roller body formed by metal working mounted on the outer race of an anti-friction bearing and a guide bolt which carries the inner raceways for the rollers inserted between it and the outer race. In this tension roller, the guide bolt has an offset section at one end formed integrally therewith which section extends through an opening in the sheet metal holder and is flanged at the free end for fastening the guide bolt and thus the tension roller to the sheet metal holder.
These known designs have a number of disadvantages and drawbacks. For example, they are comparatively bulky and heavy thereby necessitating relatively high material requirements. In addition, fastening of these known designs is not as secure and rigid as that of the present invention. Furthermore, it has been found that during the operation of these tension rollers, the belt pull on the tension roller and the torque thus generated causes the fastener to loosen and become detached due to buckling of the sheet metal holder whereby the tension roller assumes a skewed position relative to the sheet metal holder. It has also been found that special measures must be taken during the manufacturing of these tension rollers by reason of the fact that the offset fastening section of the guide bolt which must be shaped after the assembly of the roller with the holder or of the tension roller with the sheet metal holder must at the same time not be hardened. During shaping of the fastening section of the guide bolt, there is also a risk that the sheet metal holder will also be deformed whereby the accuracy, that is, the exact vertical orientation of the guide bolt relative to the sheet metal holder, is impaired.
It is, therefore, an object of the present invention to provide a tension roller assembly fastened to a holder made, for example, of sheet metal, which can be manufactured more simply and precisely, has a reduced weight and above all provides a good and permanently sure and stable connection of the components.
To this end, the tension roller assembly of the present invention comprises a guide bolt connected to a holder by riveting wherein the guide bolt is a hollow cylindrical member with an axial bore and is supported with one axial end against the front end of the sheet metal holder. The tension roller assembly further includes a fastening element separate from the guide bolt which has a radially projecting collar or the like abutting the front end of the sheet metal holder facing the guide bolt and a projection passing through the bore of the sheet metal holder and protruding into the bore of the guide bolt which projection is fixed in the bore of the guide bolt. This arrangement provides several advantages. For example, since the guide bolt is in the form of a hollow cylindrical member, it requires a relatively small amount of material and is of comparatively light weight. By this construction, it is possible to manufacture the guide bolt from a pipe section or the like. Additionally, since the fastening element is separate from the guide bolt, the guide bolt can be heat treated as a unit if necessary without having to exercise special measures to cover certain sections. The radially projecting collar of the separate fastening element with its relatively large diameter provides in turn a large contact surface on the sheet metal holder thus guaranteeing a good clamping action of the sheet metal holder between the front end of the guide bolt and the front end of the collar without deformation of the components, especially of the sheet metal holder to fasten the elements in this clamping zone. This collar, therefore, stiffens the fastening element and provides a rigid securely mounted fastening arrangement. It is also possible to produce a relatively long clamping zone; i.e., one in which there is overlap of the fastening element with the sheet metal holder and with the guide bolt which, in turn, results in a most favorable torque transmission.
There are various arrangements for securing the fastening element in the bore of the guide bolt. For example, it is possible to roll the free end of the fastening element into an annular slot in the bore of the guide bolt or to flange it behind the collar with good tension which is achievable by rolling and flanging of the individual components. Other possibilities include flexing of a clamping or expanding ring provided with claws or teeth into the surface of the projection of the fastening element or the insertion of a circlip into the annular slot on the peripheral surface of the fastening element so the clamping rings, expanding rings and circlips abut the collar of the guide bolt. In order to achieve a good tensioning of the individual components, it is desirable in the latter case to provide at least one of the axially inner lateral surfaces of the annular slot and of the circlip with lateral surfaces facing away from the collar which are inclined or wedge shaped so the expanding ring tensioning radially inwardly is pressed in the axial direction against the collar of the guide bolt thereby pressing the components against each other. Furthermore, it is possible to provide the bore of the guide bolt and the periphery of the projection of the fastening element each with cooperating thread sections. Thus, by screwing the fastening element into the tap hole of the guide bolt, the guide bolt and sheet metal holder are tensioned against one another.
In accordance with one of the illustrated embodiments, a ring-shaped axially projecting centering surface is provided in the sheet metal holder in the zone of the bore which centers the guide bolt on the sheet metal holder and the guide bolt in turn has a matching annular recess on the axial end thereof turned toward the sheet metal holder. By this arrangement, there is the additional advantage that the radial and shearing forces which act on the rollers and thus on the guide bolts are transmitted directly to the sheet metal holder without loading the fastening element.
Another feature is providing a centric bore in the tension roller which further contributes to overall weight reduction of the assembly.
The present invention has application to rollers with friction bearings and with anti-friction bearings as well. Rollers with anti-friction bearings in particular are suitable for high performance requirements and in accordance with one of the embodiments the inner raceways for the rollers are formed directly in the guide bolt and the outer race directly forms the roller body. This arrangement provides particular manufacturing advantages.